Monday 1 Jan New Year's Day
Friday 22 Apr Easter
Monday 25 Apr Easter Monday
Monday 2 May Early May Bank Holiday
Monday 30 May Spring Bank Holiday
Monday 29 Aug Summer Bank Holiday
Monday 26 Dec Christmas Day
Tuesday 27 Dec Boxing Day
Note: - On Friday 23 December and Friday 30 December 2011 all Exchange markets will close from 12:30 London time onwards.
Source: http://www.londonstockexchange.com/about-the-exchange/company-overview/business-days/business-days.htm